Three-phase induction motors have been widely recognized as workhorses of many industrial applications. Electric motors exist for different speed ranges. A high speed operation range presents certain advantages over the speed ranges possible by the direct 50/60 Hz mains frequency. Increasing the rated speed is an effective way to boost power density and efficiency. Interesting operation fields of high speed motors are applications where a gear-box and a standard motor can be replaced by a directly driven high speed motor.
The rotor of an electrical machine is usually supported by a plurality of bearings. In some instances, such as high speed rotor operation, it is beneficial to use an AMB instead of a traditional mechanical bearing. AMBs support the rotor shaft by generating a controlled magnetic flux which exerts a force on the rotor to maintain a desired rotor shaft position. The AMB is controlled by a magnetic bearing controller. Existing magnetic bearing controllers suffer from a number of shortcomings and disadvantages. There remain unmet needs including reducing hardware complexity, reducing switching losses, and increasing reliability. For instance, some magnetic bearing controllers require a large number of switches in order to step down an input voltage and provide power to a pair of windings of the magnetic bearing. In another example, some magnetic bearing controllers require isolated current sensors to calculate the appropriate amount of magnetic flux to provide to a magnetic bearing winding. There is a significant need for the unique apparatuses, methods, systems and techniques disclosed herein.